Prepared for the General Services Administration
By Dan Howett, P.E.
Oak Ridge National Laboratory
March 2015
Wireless Pneumatic Thermostat
Evaluation
Ronald Reagan Building and
International Trade Center
Washington, DC
Dan Howett, P.E.
Mahabir Bhandari, PhD
The Green Proving Ground program leverages GSA’s real estate portfolio
to evaluate innovative sustainable building technologies and practices.
Findings are used to support the development of GSA performance
specifications and inform decision-making within GSA, other federal
agencies, and the real estate industry. The program aims to drive
innovation in environmental performance in federal buildings and help
lead market transformation through deployment of new technologies.
Disclaimer
This document was prepared as an account of work sponsored by the United States Government. While this
document is believed to contain correct information, neither the United States Government nor any agency
thereof, nor Oak Ridge National Laboratory (UT-Battelle, LLC), nor any of their employees, makes any warranty,
express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any
information, apparatus, product, or process disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial product, process, or service by its trade name,
trademark, manufacturer, or otherwise, does not constitute or imply its endorsement, recommendation, or
favoring by the United States Government or any agency thereof, or Oak Ridge National Laboratory (UT-Battelle,
LLC). The views and opinions of authors expressed herein do not necessarily state or reflect those of the United
States Government or any agency thereof or Oak Ridge National Laboratory (UT-Battelle, LLC).
The work described in this report was funded by the US General Services Administration (and the Federal Energy
Management Program of the US Department of Energy) under Contract No. 2375-V544-12.
Acknowledgements
Ronald Reagan Building and International Trade Center: Bill Skocic (G4S), Greg Dix (GSA)
United States General Services Administration (GSA): Brian Schaeffer and Ian Gedalowitz
Oak Ridge National Laboratory: Mahabir Bhandari, PhD
Cypress Envirosystems: Harry Sim
Tenfold Information Design: Andrea Silvestri, Bill Freais
For more information contact:
Kevin Powell
Program Manager
Green Proving Ground
Office of the Commissioner
Public Buildings Service
US General Services Administration
555 Battery Street, Room 518
San Francisco, CA 94708
Email: kevin.powell@gsa.gov
Wireless Pneumatic Thermostat Evaluation
Page i
Table of Contents
Page
Disclaimer .................................................................................................................................................................... i
Acknowledgements ..................................................................................................................................................... i
List of Figures ............................................................................................................................................................. iii
List of Tables .............................................................................................................................................................. iii
I.
Executive Summary .......................................................................................................................................... 1
A.
B.
C.
D.
E.
II.
Background ................................................................................................................................................ 1
Overview of the Technology ...................................................................................................................... 1
Study Design and Objectives ...................................................................................................................... 2
Project Results/Findings ............................................................................................................................. 4
Conclusions and Deployment Guidelines................................................................................................... 4
Introduction ...................................................................................................................................................... 7
A. Problem Statement .................................................................................................................................... 7
B. Opportunity ................................................................................................................................................ 7
III.
Methodology .................................................................................................................................................... 8
A. Technology Description.............................................................................................................................. 8
B. Technical Objectives................................................................................................................................... 9
C. Demonstration Project Location .............................................................................................................. 10
IV.
Measurement and Verification Evaluation Plan ............................................................................................. 11
A.
B.
C.
D.
E.
V.
Facility Description ................................................................................................................................... 11
Technology Specification ......................................................................................................................... 11
Technology Deployment .......................................................................................................................... 12
Test Plan ................................................................................................................................................... 14
Instrumentation Plan ............................................................................................................................... 15
Results............................................................................................................................................................. 16
A. Technical Performance Results ................................................................................................................ 16
B. Economic Performance Results................................................................................................................ 21
VI.
Summary Findings and Conclusions ............................................................................................................... 26
A.
B.
C.
D.
VII.
Overall Technology Assessment at Demonstration Facility ..................................................................... 26
Best Practice ............................................................................................................................................. 26
Barriers and Enablers to Adoption ........................................................................................................... 27
Recommendations for Installation, Commissioning, Training, and Change Management...................... 27
Appendices ..................................................................................................................................................... 27
A. Detailed Technology Specification ........................................................................................................... 27
B. Research Details ....................................................................................................................................... 27
Wireless Pneumatic Thermostat Evaluation
Page ii
List of Figures
Figure
Page
1.
Temperature Fluctuations Under an Occupied/Unoccupied Schedule ......................................................... 10
2.
Locations of the Wireless Repeaters (indicated in red) on the Fifth Floor of the
Woodrow Wilson Center .............................................................................................................................. 13
3.
Eighth Floor Baseline (i.e., before wireless pneumatic thermostat installation)
Temperature Measurements, May 13 Through May 19, 2013 .................................................................... 16
4.
Baseline Air-Handling Unit (AHU) Supply Fan Amperage, May 13 Through
May 19, 2013 ................................................................................................................................................ 17
5.
Air-Handling Unit (AHU) Supply Fan Amperage, August 19 Through August 25, 2013 ................................. 18
6.
Eighth Floor Temperature Measurements, August 19 Through August 25, 2013 ........................................ 19
7.
Space Temperatures in an Eighth Floor Exterior Zone from December 6 Through
December 11, 2013 (nightly temperatures subfreezing) .............................................................................. 20
8.
Space Temperatures in an Eighth Floor Exterior Zone from January 6 Through
January 12, 2013 (nightly temperatures subfreezing) .................................................................................. 21
9.
Map of the 16 Climate Zones in Which the Three Building Types Were Modeled....................................... 22
10.
Results of the Energy-Savings Calculations for the Large Office in Atlanta, Georgia ................................... 23
List of Tables
Table
Page
ES-1. Standard Models of Typical Office Buildings ...................................................................................................3
ES-2. Composite Data for Simple Payback Periods ...................................................................................................4
ES-3. Performance Objectives ...................................................................................................................................5
ES-4. Greenhouse Gas Emissions for Regional and National Average Utility Fuel Mixes .........................................6
1.
Standard Models of Typical Office Buildings ................................................................................................ 14
2.
Tabulated Data for Large Office Buildings .................................................................................................... 25
3.
Tabulated Data for Medium Office Buildings ............................................................................................... 25
4.
Tabulated Data for Small Office Buildings .................................................................................................... 26
Wireless Pneumatic Thermostat Evaluation
Page iii
I. Executive Summary
A. Background
To be effective at maintaining indoor air conditions, a building heating, ventilation, and air conditioning
(HVAC) system needs to be controlled in some fashion. The control system needs to sense the temperature
of a space, feeding it to a control system, and manipulate the HVAC equipment to maintain desired
temperatures for the occupants.
Within the portfolio of buildings under the jurisdiction, custody, or control of the General Services
Administration (GSA), approximately 20% have HVAC systems that are operated by pneumatic control
systems. These buildings are under the same energy conservation mandates as all federal facilities.
Unfortunately, the major drawback to pneumatic systems is that they are not capable of implementing
automated energy-saving control strategies. They can’t automatically change the thermostat setting at
night and on weekends in the same way as more modern control systems such as direct digital controls
(DDCs). Converting a building from a pneumatic control system to DDCs is typically cost prohibitive.
The wireless pneumatic thermostat (WPT) is a new technology designed to mimic the capabilities of DDCs.
Vendors claim WPTs can be retrofitted to existing pneumatic control systems in a cost-effective fashion.
WPTs allow facilities to exercise energy-saving control strategies such as setting thermostats back at night.
If capable of satisfactorily performing such functions, the WPT could be a valuable technology for use in GSA
and other facilities to help reduce energy consumption and meet related goals.
The purpose of this study is to evaluate the ability of the WPT to implement energy-saving control strategies
in an actual building that currently has a pneumatic control system. If this ability is proven in a field
demonstration, energy modeling will be used to estimate the potential energy savings and economic
benefits from this technology in typical buildings across the GSA portfolio.
B. Overview of the Technology
The core piece of equipment in a pneumatic HVAC control system is the thermostat, which mounts to the
wall of a space, detects space temperature, and sends this information via pneumatic tubing to the HVAC
system.
The WPT technology operates from a straightforward premise: replace the conventional pneumatic
thermostat with a device that not only detects space temperature and sends information via existing
pneumatic tubing, but also can be adjusted and controlled by a central energy management system (EMS)
through a wireless network. By using the EMS to control thermostat settings wirelessly, the building
manager is able to implement energy-saving control strategies heretofore not possible with conventional
pneumatic controls.
As an example, look at a typical office space where indoor temperature is maintained at 72°F. Below that
point the HVAC system provides warm air to the space, and above that point cool air is supplied. With a
conventional pneumatic control system, the HVAC system will maintain these conditions all day, every day,
and on weekends and holidays too. That is because the thermostats are mechanical devices that must be
manually adjusted to change their settings. True, an HVAC technician could walk around every night and
morning to manually change the temperature to a more energy-saving setpoint, but that is expensive in
terms of labor costs.
Wireless Pneumatic Thermostat Evaluation
Page 1
With the WPT technology installed, the manufacturer claims that the space temperature settings can be
changed automatically through the central EMS. If the EMS is programmed, the building’s thermostats can
be set back to a range of 68°F to 79°F at 5:00 p.m., when occupants go home. They can then be reset to
72°F and 75°F at 7:00 a.m. to make the space more comfortable as occupants return. In this fashion, the
building’s HVAC system will not work as hard overnight and thereby save energy.
By implementing a control strategy such as this (commonly called an “occupied/unoccupied schedule”), the
HVAC system keeps occupants comfortable while they are in the building but allows energy to be saved
when the building is not occupied. Energy saving goals are supported, and a site’s utility costs go down.
The commercial potential for this product, if these energy-/cost-saving claims are verified, is substantial. As
said before, 20% of GSA buildings use pneumatic devices to control their HVAC systems. Pneumatics are
typically used in existing buildings built before 1999 that are multistory and more than 20,000 ft2. It is less
common to see pneumatic control systems in single story offices, strip malls, or big-box retail
establishments as they typically use rooftop units that directly control the space below. Smaller buildings,
less than 20,000 ft2, also tend to use packaged units rather than a central plant with zone thermostat
control.
C. Study Design and Objectives
The Woodrow Wilson Center (WWC) was selected as the site to demonstrate the WPT technology. The
center is located within the Ronald Reagan Building and International Trade Center in Washington, DC. This
demonstration site was selected for several reasons. First, its HVAC system is controlled by a fairly new
pneumatic control system (the building opened in 1998) that functions well. A system such as this
represents the type which the WPT technology can be installed on to improve performance.
Second, WWC floor space consists of a variety of office spaces, including individual offices, conference
rooms, open cubicles, and common areas. This type of mixed use is typical in the majority of facilities under
GSA control.
Third, the evaluation team had complete access to all areas so that they could take measurements, install
data loggers, and freely evaluate how well the WPT performed its tasks. The space at WWC had no “secure
areas” that were off limits to the evaluation team.
The evaluation of the WPT technology consisted of two stages, a performance evaluation followed by an
energy and economic evaluation. The former would be conducted at WWC. The latter would be
accomplished via computer modeling of energy use and economics.
The goal for the performance evaluation was to answer the question, “Does the WPT technology have the
ability to control the thermostat temperature settings in individual spaces?” The plan for the performance
evaluation is very straightforward. Temperature data loggers would be placed in select spaces at WWC to
record space temperatures in 5-minute intervals. These loggers would record space temperatures during
two phases. First, temperatures would be logged when the space was being controlled by the existing
pneumatic control system. These data would be graphed and the temperature pattern noted.
Second, the WPT system would be installed under a turnkey contract, an occupied/unoccupied schedule
would be set by the technology’s controller, and the building’s space temperatures again logged. If the WPT
were operating as promised, the loggers would see the space temperatures change during the unoccupied
Wireless Pneumatic Thermostat Evaluation
Page 2
hours to a more energy-conserving setpoint. In the winter, the spaces would grow colder. In the summer,
spaces would grow warmer.
If the WPT passed the performance test and proved that it had the ability to control space temperatures
remotely and implement energy-saving control strategies on a pneumatic control system, the economic
evaluation would be implemented.
The energy and economic evaluation goal was to answer the question, “Given the ability to exercise energysaving control strategies, how much energy could potentially be saved by operating an occupied/unoccupied
schedule on typical buildings in the GSA portfolio located in various places around the country?”
To answer this question, Oak Ridge National Laboratory (ORNL) researchers would use the DOE-2 energy
modeling software to calculate potential energy savings. Within the program, ORNL would look at the three
standard models of “typical” office buildings shown in Table ES-1.
Table ES-1. Standard Models of Typical Office Buildings
(used in energy-savings calculations)
Area
2)
(ft
Floors
Window to
Wall Ratio
(%)
Plug Load
2
(W/ft )
Lighting
2
(W/ft )
Small Office
5,500
1
21
1
1.8
Medium Office
53,630
3
33
1
1.6
Large Office
498,500
12
38
1
1.5
Building Type
These models were developed by Pacific Northwest National Laboratory in conjunction with the
US Department of Energy (DOE) and are widely used as standards when modeling various energy-saving
technologies and techniques.
Each of the three models would be evaluated in 16 different cities with their respective climate patterns.
For each combination of building type and city (e.g., a small office located in Houston, Texas), the energy
consumption would be modeled using five different thermostat schedules. The baseline would calculate
energy consumption if the thermostat settings were set to 69°F heating and 75°F cooling, with no setbacks
at night or on weekends.
For comparison, the model would then be run four more times; each time the unoccupied thermostat
setting would be changed to a more energy-saving unoccupied setting from 6:00 p.m. to 6:00 a.m. The
thermostat setting combinations would be as follows.
•
66°F heating and 79°F cooling
•
62°F heating and 83°F cooling
•
58°F heating and 87°F cooling
•
54°F heating and 91°F cooling
The cooling and heating energy consumption for each unoccupied setting would be compared to the
baseline consumption. The savings would be calculated and displayed in both graphical and tabular form for
Wireless Pneumatic Thermostat Evaluation
Page 3
use by GSA building managers considering installation of the WPT technology. (Note: Tables and graphs of
results are shown in Appendix B.)
D. Project Results/Findings
In this project, data gathered showed that the WPT technology does, in fact, have the ability to implement
energy-saving control strategies on HVAC systems that use pneumatic control systems. Further, economic
analysis showed that the technology is financially viable across a wide spectrum of typical facilities. It should
be noted that energy modeling looked at the energy-saving potential of only the most basic
occupied/unoccupied control strategy. If other strategies are implemented, the potential for energy savings
is much greater, with an even greater financial viability of the technology.
Table ES-2 gives a summary of the financial simple paybacks that were derived from the energy modeling
and economic analysis. (The following installation costs were used to generate the payback ranges: small
office, $3,850 to $6,600; medium office, $32,200 to $59,000; large office, $249,000 to $449,000.)
Table ES-2. Composite Data for Simple Payback Periods
2
Climate
Zone
City
Large Office (498,500 ft )
Simple Payback Range
(years)
2
Medium Office (53,630 ft )
Simple Payback Range
(years)
2
Small Office (5,500 ft )
Simple Payback Range
(years)
Low
High
Low
High
Low
High
1A
Miami, FL
3.6
6.5
3.7
6.8
1.9
3.3
2A
Houston, TX
3.7
6.7
4.5
8.2
2.9
5.0
2B
Phoenix, AZ
4.6
8.2
4.0
7.3
2.5
4.3
3A
Atlanta, GA
3.0
5.4
3.5
6.4
2.6
4.5
3B-coast
Los Angeles, CA
2.8
5.1
3.7
6.8
3.7
6.3
3B
Las Vegas, NV
5.3
9.5
5.0
9.2
3.1
5.4
3C
San Francisco, CA
3.0
5.5
3.8
7.0
3.2
5.5
4A
Baltimore, MD
2.8
5.0
3.3
6.0
2.7
4.7
4B
Albuquerque, NM
5.4
9.7
6.0
10.9
3.5
5.9
4C
Seattle, WA
3.6
6.5
4.5
8.2
4.3
7.4
5A
Chicago, IL
3.1
5.6
3.8
7.0
2.8
4.8
5B
Boulder, CO
5.0
8.9
5.7
10.5
3.7
6.4
6A
Minneapolis, MN
4.6
8.3
5.7
10.5
3.7
6.3
6B
Helena, MT
3.9
7.1
4.6
8.4
3.3
5.7
7
Duluth, MN
4.3
7.8
5.3
9.7
3.7
6.3
8
Fairbanks, AK
4.2
7.6
5.2
9.5
3.1
5.3
E. Conclusions and Deployment Guidelines
WPTs have strong potential to support energy savings in a variety of federal and commercial facilities
(Table ES-3).
Deployment Priority 1 would be any facility that currently has a pneumatic HVAC control system that is
operating properly. While this may sound like an oversimplification of the situation, the WPT technology is
Wireless Pneumatic Thermostat Evaluation
Page 4
such that it has potential to help any building of this type, and individual factors should be evaluated for
each individual building.
Deployment Priority 2 should be facilities that have high per-unit costs of energy, especially if they have high
dollar-per-kilowatt-hour costs.
There does not appear to be a Deployment Priority associated with a particular climate zone. The
technology appears to work equally well across the spectrum of climate zones.
Table ES-3. Performance Objectives
Quantitative
Objectives
Metrics and Data
Requirements
Success Criteria
Exercise wireless
control over HVAC
systems controlled by
pneumatic control
systems.
Space temperatures are
measured under
baseline and test
conditions to
determine whether
their temperatures do,
in fact, change based
upon the wireless
pneumatic thermostat
(WPT) technology
providing that control.
If successful, the
space
temperatures
would show a
pattern of change
consistent with
the energy-saving
control strategy
that the WPT was
programmed to
implement.
Reduce Costs
Cost reduction will be
through reduced
energy consumption
and costs that are a
result of the
technology’s ability to
exercise control
strategies.
Reduce Emissions
Emission reductions will
be through reduced
energy consumption.
Measurement and
Verification Results
Best-Case
Deployment Scenario
Space temperature
logs did show the
temperature changes
that indicate that the
WPT technology can
control space
temperatures and
operate energysaving strategies.
A building with a
properly operating
pneumatic control
system in a city with
high per-unit utility
costs would be the best
candidate to have this
technology deployed.
Qualitative Objectives
Ease of Installation
Feedback from
No major
maintenance personnel problems
during installation.
reported during
installation.
Feedback was
positive from
personnel.
Ease of Use
Maintenance logs
during operation.
Customer has
reported positive
experiences with the
technology.
Wireless Pneumatic Thermostat Evaluation
No problems
reported during
use.
Page 5
Table ES-4. Greenhouse Gas Emissions for Regional and National Average Utility Fuel Mixes
(kg CO 2 equivalent/f2/year)
Regional Utility Fuel Mix
National Utility Fuel Mix
Baltimore, Maryland
Site
0.435
0.466
Atlanta, Georgia
0.650
0.516
San Francisco, California
0.094
0.165
Note: Greenhouse gas (GHG) figures calculated from energy savings for a single building, as determined through energy
2
modeling conducted as part of this study. Parameters were a large office building (495,000 f ) at 16°F setback during
unoccupied hours. GHG per kilowatt-hour savings found in the US Environmental Protection Agency’s eGrid, 9th ed.,
Version 1.0, Year 2010 Summary Tables.
Wireless Pneumatic Thermostat Evaluation
Page 6
II. Introduction
A. Problem Statement
To be effective at maintaining indoor air conditions, a building heating, ventilation, and air conditioning
(HVAC) system needs to be controlled in some fashion. In simplest terms, there needs to be a way of
sensing the temperature of a space, feeding that information to a control system, and then manipulating the
HVAC equipment so that the space temperature is maintained within a comfortable range for the occupants.
From the early twentieth century into the 1980s, the principal technology for performing this task in large
buildings was the pneumatic control system. Systems of this type use pressurized air in various components
to both detect space conditions and to operate the HVAC equipment that serves the area. Pneumatic
control systems were state-of-the-art before the development of electronic and digital control systems.
The major drawback to pneumatic systems is that they are not capable of implementing automated energysaving control strategies. They cannot automatically change the thermostat setting at night and on
weekends or detect whether a person is in the space and needs the “occupied” temperature setting.
Currently, a more modern control system such as direct digital controls (DDCs) is required to perform such
energy-saving functions. Converting a building from a pneumatic control system to DDCs is typically cost
prohibitive due to significant modifications required within the building.
The wireless pneumatic thermostat (WPT) is a new technology designed to mimic the capabilities of DDCs.
Vendors claim WPTs can be retrofitted to existing pneumatic control systems in a cost-effective fashion.
WPTs allow a facilities to exercise energy-saving control strategies such as setting thermostats back at night.
If capable of performing such functions, the WPT could be a valuable technology for use in US General
Services Administration (GSA) and other facilities to help reduce energy consumption and meet related
goals.
The purpose of this study is to evaluate the ability of the WPT to implement energy-saving control strategies
in an actual building that currently has a pneumatic control system. If this ability is proven in a field
demonstration, energy modeling will be used to estimate the potential energy savings and economic
benefits from this technology in typical buildings across the GSA portfolio.
B. Opportunity
Within the portfolio of buildings under the jurisdiction, custody, or control of GSA, about 20% have HVAC
systems that are operated by pneumatic control systems. These buildings are under the same energy
conservation mandates as all federal facilities. Also, based on anecdotal observations, about 25% of
commercial office space is still controlled by pneumatic control systems. In other words, energy-saving
control strategies for HVAC systems in about one-fourth of domestic office buildings cannot be implemented
with their current controls technology.
According to the US Department of Energy (DOE), within the American commercial building sector, space
heating, cooling, and ventilation account for 3.75 quads of energy consumption per year. This is roughly
equal to the energy found in 135,000,000 tons of coal. (Note:
1 quad = 1015 Btu or
1,000,000,000,000,000 Btu.)
Using rough figures, if 25% of commercial buildings (a conservative estimate of those currently served by
pneumatic controls) could exercise energy-saving strategies and save just 10% per year on HVAC costs,
about 0.0938 quads (93.8 × 1012 Btu) could be saved per year.
Wireless Pneumatic Thermostat Evaluation
Page 7
The WPT technology is supposed to be able to provide the capability of exercising such control strategies.
A literature search showed that the WPT technology is available from at least two vendors. This technology
has been commercially available since 2008.
The major benefit claimed for this technology is the ability to implement energy-saving control strategies as
described above.
The technology has not been widely deployed yet. Some leading-edge companies have installed the
technology within a few buildings, but a literature search showed no third-party evaluations that had been
conducted to date.
There is relatively little risk of implementing this technology. Should a facility install WPTs, and the devices
not work as advertised, it is a simple matter to remove the devices and reinstall the original pneumatic
thermostats that were in the building. There is virtually no risk of the technology causing an “incident”
which causes damage to a facility.
One barrier to deploying this technology is the fact that it uses wireless signals to communicate with the
thermostats. Certain facilities have restrictions on what sort of wireless receivers and transmitters can be
used therein, typically due to security reasons. If a facility has security restrictions of this type, it will be
important to evaluate the technology from a security perspective before proceeding with installation.
III. Methodology
A. Technology Description
The core piece of equipment in a pneumatic HVAC control system is the thermostat, which mounts to the
wall of a space, detects space temperature, and sends this information via pneumatic tubing to the HVAC
system. The HVAC system can then provide warm or cool air to the space to adjust the temperature to a
comfortable range.
The WPT technology operates from a straightforward premise: replace the conventional pneumatic
thermostat with a device that not only can detect space temperature and send information via existing
pneumatic tubing, but also can be adjusted and controlled by a central energy management system (EMS)
through a wireless network. By using the EMS to wirelessly control thermostat settings, the building
manager is then able to implement energy-saving control strategies heretofore not possible with
conventional pneumatic controls.
As an example, look at a typical office space where indoor temperature is maintained between 69°F and
75°F. Below that range the HVAC system provides warm air to the space, and above that range cool air is
supplied. With a conventional pneumatic control system, the HVAC system will maintain these conditions all
day, every day, including weekends and holidays too. That is because the thermostats are mechanical
devices that must be manually adjusted to change their settings. True, an HVAC technician could walk
around every night and morning to manually change the temperature to a more energy-saving setpoint, but
that is expensive in terms of labor.
With the WPT technology installed, the manufacturer claims that the space temperature settings can be
changed automatically through a central EMS. If the EMS is programmed, the building’s thermostats can be
set back to a range of 65°F to 79°F at 5:00 p.m. when occupants go home. They can then be reset to 69°F
Wireless Pneumatic Thermostat Evaluation
Page 8
and 75°F at 7:00 a.m. to make the space more comfortable as occupants arrive. In this fashion, the building
HVAC system will not work as hard over night and thereby save energy.
By implementing a control strategy such as this (commonly called an “occupied/unoccupied schedule”), the
HVAC system keeps occupants comfortable while they are in the building but allows energy to be saved
when the building is not occupied. Energy saving goals are supported, and a site’s utility costs go down.
The commercial potential for this product, if its claims are verified, is substantial. As said before, 20% of GSA
buildings use pneumatic devices to control their HVAC systems. Informal surveys indicate that the ratio of
commercial buildings with pneumatic systems is roughly the same.
B. Technical Objectives
The principal question to be evaluated within this study is, “Does the WPT technology have the ability to
implement energy-saving control strategies on an HVAC system that heretofore was controlled solely by a
conventional pneumatic control system?”
To test this question, the WPT system will be programmed such that an “occupied-unoccupied” thermostat
schedule will be implemented. That is to say, the space temperature will be maintained within normal
comfort settings during hours when the building is occupied, but it will be allowed to drift to a point where
energy is conserved when the space is unoccupied.
The metric which will answer this question is the ambient temperature inside offices within the selected
buildings. Data loggers will be used to keep track of the temperature in 5-minute intervals, 24 hours/day.
Before installation of the WPTs, data loggers should show that space temperatures are maintained within a
relatively narrow band all day, every day. After the WPT system is installed, space temperatures should
show a pattern where they maintain that same narrow temperature band during the day, but at night and
on weekends the temperatures swing to a wider point (warmer in summer and cooler in winter) that can be
maintained while consuming less energy in the HVAC system.
Figure 1 is an example of what happens to space temperatures when an occupied-unoccupied schedule is in
place. The figure shows the summer interior space temperatures of a GSA facility in Phoenix, Arizona. This
facility has a DDC system with an aggressive occupied/unoccupied thermostat schedule. During the day,
space temperatures are maintained between 75°F and 77°F, but at night conditions are allowed to drive the
temperature as high as 84°F. The graph shows 5 weekdays where temperatures are maintained in the close
range. Each night, the HVAC system is adjusted so that space temperatures can rise while not requiring
much energy from the HVAC system. At around 5:00 a.m. each weekday, the controls system calls for the
HVAC system to lower the temperature back to the tighter range so that occupants are comfortable. During
the weekend, temperatures are allowed to drift widely before being reset on Monday morning.
If data recorded by the temperature loggers show that the WPT technology demonstrates an ability to
exercise this occupied/unoccupied energy-saving schedule, energy modeling will be used to evaluate the
potential for saving energy and energy costs at representative GSA facilities in 16 climate zones around the
country. Details of this economic analysis are included in Section IV., “Measurement and Verification
Evaluation Plan.”
Wireless Pneumatic Thermostat Evaluation
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Figure 1. Temperature Fluctuations Under an Occupied/Unoccupied Schedule.
C. Demonstration Project Location
To find an ideal location for evaluating WPT performance, the following criteria were used to screen
potential buildings.
•
Does the building have well-operating pneumatic controls on its HVAC system?
•
Does the building have a variety of offices that are consistent with what is found in most GSA buildings?
•
Will the evaluation team have access to the office areas in order to install data loggers to measure
trends in space temperatures and humidities?
•
Will the evaluation team have access to the air handlers and other mechanical equipment that serve the
spaces in question?
•
Are there any restrictions that would prohibit using wireless technology within the building? For
example, some federal agencies have “secure areas” that impact the use of such technologies in
surrounding spaces.
With these criteria, GSA regions around the country were asked to submit candidate facilities for
consideration.
Wireless Pneumatic Thermostat Evaluation
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IV. Measurement and Verification Evaluation Plan
A. Facility Description
The Woodrow Wilson Center (WWC) was selected as the site to demonstrate the WPT technology. The
center is located within the Ronald Reagan Building and International Trade Center in Washington, DC. This
demonstration site was selected for several reasons. First, its HVAC system is controlled by a fairly new
pneumatic control system that functions well. A system such as this represents the type upon which the
WPT technology can be installed to improve performance.
Second, the WWC floor space consists of a variety of office spaces. Within the mix are individual offices,
conference rooms, open cubicles, and common areas throughout the space. This type of use is typical of
what is found in the majority of facilities controlled by GSA.
Third, the evaluation team had complete access to all areas so that they could take measurements, install
data loggers, and freely evaluate how well the WPT performed its tasks. The space at WWC had no secure
areas that were off limits to the evaluation team.
The specific areas of the WWC used for the demonstration were Floors 3–8. Each floor has about 15,000 ft2
of space. The north, east, and south sides of the WWC are exterior walls. The west side leads into another
interior space.
The evaluated technology was installed solely as part of the demonstration/evaluation project.
B. Technology Specification
The WPT system consists of three primary components.
The first component is the WPT, which replaces the conventional pneumatic thermostat. This device is
installed on the wall of a given HVAC zone, and it connects to the existing pneumatic tubing that previously
connected the standard thermostat to the facility’s HVAC control system. Included within this component is
a means to electronically measure the space temperature, a device which translates this data to a
pneumatic signal to interface with existing controls, and a wireless transmitter/receiver to interact with
other thermostats and the WPT technology’s central controller.
The second component of this system is the central controller. This device interacts with the wireless
thermostats mentioned in the previous paragraph and controls their settings. It should be noted that the
central controller can operate as a stand-alone device that is not directly integrated with the facility’s
building automation system. When operating in this stand-alone configuration, it can perform the following
energy-saving control strategies.
•
Programmable scheduled occupied/unoccupied setpoints
•
Temperature setpoint policy enforcement (high/low limits)
•
Ongoing commissioning alarm/notification and automatic calibration
•
Deadband (heat below and cool above setpoints)
Wireless Pneumatic Thermostat Evaluation
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•
Zone level automated demand response using OpenADR (i.e., Open Automated Demand Response
Communication Standards)
•
Zone level precooling and load shifting/peak reduction
The central controller can also be integrated with a facility’s building automation system. When operated in
this mode, additional energy-saving control strategies can be implemented.
•
Optimal start-stop
•
Supply air/chilled water temperature reset
•
Duct static pressure reset (throttling variable frequency drive fans)
•
Central plant level auto-demand response.
The third component of the WPT system is a wireless repeater. These devices are placed throughout the
facility to ensure that wireless signals are transmitted reliably between the thermostats and the central
controller.
The vendor provided an estimate of installation costs for this system. These estimates are based upon the
proposed facility’s total floor area.
•
Small buildings (<10,000 ft2): $0.70–$1.20/ft2
•
Medium buildings (between 10,000 and 300,000 ft2): $0.60–$1.10/ft2
•
Large buildings (>300,000 ft2): $0.50 –$0.90/ft2
Several factors can influence whether an installed price is near the higher or lower range of these estimates.
The single biggest factor is the density of wireless thermostat devices needed for a facility. If there are a
large number of individual offices, each with its own HVAC zone and thermostat, the cost will tend to be
higher. On the flip side, in a facility with large open areas served by a single HVAC zone, the cost will tend to
be lower.
A secondary factor that influences the price is local labor rates to install the technology.
The third factor is the facility’s construction type. If its walls are made of plaster or block, as opposed to
conventional drywall, it will take more time and cost more to install each wireless thermostat. Also, a
heavier construction type such as concrete will impede the transmission of wireless signals. This will dictate
that more wireless repeater devices be installed to be able to transmit the signals reliably.
C. Technology Deployment
The WPT system was deployed on six floors of the WWC.
During the first step of installation, the technology vendor evaluated the building, its six floors, and various
areas of each floor to determine the quantity, type, and locations of conventional pneumatic thermostats
that would need to be replaced with its wireless device. The vendor also evaluated the building to
determine how well wireless signals could be transmitted through various structural elements on each floor.
This information, coupled with the thermostat locations, gave the vendor information to determine how
many wireless repeaters would be needed and where to locate them.
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The second step was to determine where to locate the central controller. This decision is based upon having
a location that supports its ability to communicate with the wireless repeaters. Also, the central controller
needs to be located appropriately to communicate with the computer or building management system.
The third step was to install the wireless thermostats in place of the existing pneumatic devices. This step
took about 30 minutes per thermostat and did not require any special skills beyond those that a trained
HVAC technician should possess. This step was followed by installation of the wireless repeaters and the
central controller.
Finally, the vendor commissioned the entire WPT system to ensure that all connections were working
properly.
Figure 2 shows the locations of the wireless repeaters (in red) on the fifth floor of the WWC. It is
representative of locations found on the other five floors which were tested. The central controller was
located on the fourth floor near an existing hub to the building management system. Thermostats were
located one per zone.
Figure 2. Locations of the Wireless Repeaters (indicated in red) on
the Fifth Floor of the Woodrow Wilson Center. (The fifth floor is
representative of the other floors.)
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D. Test Plan
The evaluation of the WPT technology consisted of two stages, a performance evaluation followed by an
economic evaluation. The former would be conducted at the WWC. The latter would be accomplished via
computer modeling of energy use and economics.
The performance evaluation’s goal was to answer the question, “Does the WPT system have the ability to
control the thermostat temperature settings in individual spaces and to operate them using energy-saving
control strategies?”
If the central controller could perform this task satisfactorily, then building managers would have a new
technology that would allow them to conserve energy without having to replace their entire pneumatic
control system.
The plan to conduct the performance evaluation is straightforward. Temperature data loggers would be
placed in select spaces at the WWC to record space temperatures in 5-minute intervals. These loggers
would record space temperatures during two phases. First, temperatures would be logged when the space
was being controlled by the existing pneumatic control system. This data would be graphed and the
temperature pattern noted.
Temperature data would be downloaded from the data loggers by GSA personnel and transmitted to Oak
Ridge National Laboratory (ORNL) for analysis.
Second, the WPT system would be installed, an occupied/unoccupied schedule would be set by the
building’s management system, and the building’s space temperatures again logged. If the WPT were
operating as promised, the loggers would see the space temperatures change during the unoccupied hours
to a more energy-conserving setpoint. In the winter, the spaces would be allowed to grow colder. In the
summer, spaces would be allowed to grow warmer.
If the WPT passed the performance test and proved that it had the ability to control space temperatures
remotely and implement energy-saving control strategies on a pneumatic control system, the economic
evaluation would be implemented.
The economic evaluation’s goal was to answer the question, “Given the ability to exercise energy-saving
control strategies, how much energy could potentially be saved by operating an occupied/unoccupied
schedule on typical buildings in the GSA portfolio located in various places around the country?”
To answer this question, ORNL researchers would use the DOE-2 energy modeling software to calculate
potential energy savings. Within the program, ORNL would look at three standard models of “typical” office
buildings, described in Table 1.
Table 1. Standard Models of Typical Office Buildings
(used in energy-savings calculations)
Building Type
Area
2
(ft )
Floors
Window to
Wall Ratio
(%)
Plug Load
2
(W/ft )
Lighting
2
(W/ft )
Small Office
5,500
1
21
1
1.8
Medium Office
53,630
3
33
1
1.6
Large Office
498,500
12
38
1
1.5
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These models were developed by the Pacific Northwest National Laboratory in conjunction with DOE and
are widely used as standards when modeling various energy-saving technologies and techniques.
Each of the three models would be evaluated in 16 different cities with their respective climate patterns.
For each combination of building type and city (e.g., a small office located in Houston, Texas), the energy
consumption would be modeled using five different thermostat schedules. The baseline would calculate
energy consumption if the thermostat settings were set to 69°F heating and 75°F cooling, with no setbacks
at night or on weekends.
For comparison, the model would then be run four more times; each time the unoccupied thermostat
setting would be changed to a more energy-saving unoccupied setting from 6:00 p.m. to 6:00 a.m. The
thermostat setting combinations would be as follows.
•
66°F heating and 79°F cooling
•
62°F heating and 83°F cooling
•
58°F heating and 87°F cooling
•
54°F heating and 91°F cooling
The cooling and heating energy consumption for each unoccupied setting would be compared to the
baseline consumption. The savings would be calculated and displayed in both graphical and tabular form for
use by GSA building managers considering installation of the WPT technology. (Tables and graphs of results
are shown in Appendix B.)
It should be noted that while the modeling effort focused on a straightforward occupied/unoccupied control
strategy, the WPT technology is capable of several other strategies that have potential to save more energy
than the one modeled. These strategies were discussed earlier in Section IV.B., “Technology Specification.”
E. Instrumentation Plan
The instrumentation plan consisted of installing temperature data loggers within the building. The HVAC
zones initially selected were high-traffic common areas where most occupants could be expected to spend
time during any given day.
The variables being monitored by these loggers were space temperature and relative humidity. The
expected range of temperatures measured was between 55°F and 90°F. The expected range of relative
humidity was 30%–90% RH.
Note: The initial instrumentation plan called for data loggers to be placed on the air handlers serving the
WWC to record data points such as chilled water flow rate, chilled water temperature differences, fan
amperage, and the like. The purpose was to try and quantify a change in HVAC energy consumption due to
installation of the WPT system. After initial analysis of this, it became apparent that it would be near
impossible to isolate what energy changes were due solely to the WPT technology. Therefore, these data
were set aside and the study focused on using space temperatures to validate whether the WPT system
could actively control thermostat settings and execute energy-saving control strategies.
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V. Results
A. Technical Performance Results
Collection of temperature data, without the WPT installed, began in February 2013. From February until
May, temperature and humidity data were collected from spaces. As mentioned before, data were also
collected from the air handlers serving this area.
In June 2013, the WPT system was installed at the WWC, and data were collected by the loggers during the
summer months.
In September 2013 a preliminary data analysis meeting was held among all parties. Figures 3–6 are from
that meeting and summarize the data up to that time. A discussion follows the images.
Figure 3. Eighth Floor Baseline (i.e., before wireless pneumatic thermostat installation)
Temperature Measurements, May 13 Through May 19, 2013.
The baseline space temperature data (Figure 3) were exactly what was expected. The temperature varied
within a narrow band (72°F–74°F). On weekends, the temperature lingered at the low end of this band due
to the lack of internal heat sources (people, office equipment, lights) that would be present during
weekdays.
The baseline air-handling unit (AHU) supply fan amperage (Figure 4) also showed what was expected. As the
space temperatures slowly heated due to occupants entering, office electronics turning on, sunlight entering
the windows, and outside air warming, the air handler slowly changed its output to provide appropriate
cooling to the space. It’s important to emphasize that the air handler output was changing slowly. This is
due to the fact that the temperature setpoint in the space remained constant, and the heat inputs
(occupants, electronics, etc.) were changing slowly.
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Figure 4. Baseline Air-Handling Unit (AHU) Supply Fan Amperage, May 13 Through May 19,
2013.
After installation of the WPT system, the technology was programmed so that the temperature settings
would change based upon the time of day and week when the space was most likely to be occupied.
Between 6:00 a.m. and 7:00 p.m., the temperature was controlled between 70°F and 75°F to keep
occupants comfortable. However, between 7:00 p.m. and 6:00 a.m., temperatures were allowed to float
between 68°F and 80°F, thereby reducing the load on the HVAC system and the amount of energy
consumed by it.
The initial set of data collected after installation of the WPT system showed some unusual findings. The first
observation came when looking at data from the AHU supply fan amperage (Figure 5). In this graph, the
amperage draw showed distinct jumps occurring on a cyclical daily basis. The team looked at all factors that
might be causing these rhythmic patterns and what might have changed between the baseline and test
periods. The building occupancy and office electronics had stayed the same. Exterior sunlight was coming
through windows at a higher angle than during the baseline. However, the sun still rose, moved across the
sky, and set in a predictably constant pattern and could not have caused the step changes seen in the air
handler power graph. Outside air temperature was warmer during the test period than the baseline period.
But as with the sunlight angle, it still changed in a slow pattern and would not have caused what the data
were showing.
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Figure 5. Air-Handling Unit (AHU) Supply Fan Amperage, August 19 Through August 25, 2013
(initial data collected after installation of wireless pneumatic thermostat).
After sorting through variables, it was determined that the only thing that would cause the rhythmic step
changes in power draw would be for the space temperature setpoint to be changed on a daily schedule. As
part of installing the WPT system, the cooling temperature setpoints in the spaces were set at 75°F during
the occupied day period but allowed to drift to 80°F at night. As the setpoint jumped back and forth
between the two, the air handler fan would see a sudden change in fan power draw, which is what is
reflected in the graph.
This daily pattern of fan amperage change was a clear indication that the WPT system was exercising active
control over space temperatures.
However, looking over the space temperature graphs from the data loggers showed that most of the
temperature loggers did not show a dramatic pattern of space temperature changes consistent with an
occupied/unoccupied schedule. (Figure 6 is typical of the temperature data that were gathered.) The
temperatures remained consistent throughout the day, night, and weekends. It was as if the WPT system
were not exercising any sort of energy-saving thermostat schedule. These data were puzzling to the
research team, especially in light of the air handler fan power readings, which gave clear indication that the
thermostats were being adjusted on a daily basis.
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Figure 6. Eighth Floor Temperature Measurements, August 19 Through August 25,
2013 (initial data collected after installation of wireless pneumatic thermostat).
The team explored deeper into this issue and noticed that the temperature loggers that showed this odd
trend were all located in areas that were in interior HVAC zones. There were common areas where many
people walked and worked during the day, but at night and on weekends they were empty. No electronics
were operating. Lights were turned off. No people walking through. In short, there were no heat sources
within the space to possibly push the space temperature higher, toward the unoccupied setpoint. Also,
WWC is constructed of concrete and steel, which surrounded the interior spaces. This caused these areas to
have a high thermal mass, which would further slow down changes in temperature within the spaces.
As part of the technology evaluation, the team wanted tangible evidence that the WPT system was allowing
space temperatures to fluctuate on an energy-saving schedule, and these data sets did not provide that
evidence. After considering all options, the team decided to move the temperature data loggers to exterior
zones and continue measuring temperature. In exterior zones during unoccupied periods, space
temperature would still be influenced by the outside air temperature and sunlight coming through the
windows. Even when the space had no people or electronics to change the space temperature, there were
factors that would cause temperature changes to show up on the data loggers. Also, because the exterior
zones had a wall with large glass surfaces instead of being surrounded by concrete and steel, the zones
would have less thermal mass, and therefore the temperatures would tend to change more rapidly based
upon other heat sources.
The data loggers were moved in October 2013 to exterior zones. October has moderate temperatures in
Washington, DC, but data were set to be collected through the winter months. The team reasoned that if
the WPT were exercising an occupied/unoccupied schedule, the space temperature at night and on
weekends would go lower than during the day. If the WPT system could demonstrate the ability to exercise
this energy-saving control strategy during the winter, it would follow logically that it could also execute such
a strategy during the summer when space temperatures would go higher when unoccupied.
Wireless Pneumatic Thermostat Evaluation
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As fortune would have it, the winter of 2014 was one of the coldest on record in Washington, DC, and gave a
perfect opportunity to see whether the WPT system could control space temperatures and exercise the
occupied/unoccupied schedule. If it were doing so, exterior space temperature logs would show a clear
pattern of comfortable temperatures during the day but cooler space temperatures at night, which reduces
the amount of heat energy needed.
Figure 7 shows space temperatures as they were in an eighth floor exterior zone from Friday, December 6,
through Wednesday, December 11, 2013. In this figure, one sees that space temperatures declined during
the unoccupied weekend such that they were maintained between 70.0°F and 69.5°F. Around 6:00 a.m.
Monday, the WPT technology initiated a controls sequence that requested the HVAC system raise the space
temperature to its occupied setting. The temperature recorder shows the distinct change in temperature at
this time.
Figure 7. Space Temperatures in an Eighth Floor Exterior Zone from December 6 Through
December 11, 2013 (nightly temperatures subfreezing).
During the occupied hours, the temperature stayed consistently at 70.5°F. For the temperature to stay so
consistent and not fluctuate within the dead band indicates that there was sufficient heat loss within the
room such that the room’s HVAC system had to constantly provide heat just to maintain it at this lower
point of the thermostat range.
If there had been a large heat source inside the room, such as sunlight through a window, large electronics,
or a lot of people, the temperature would have fluctuated more within the occupied temperature dead
band and would have risen above 70.5 for parts of the day.
Around 6:00 p.m. on Monday, December 9, the WPT technology initiated a step change that allowed the
space temperature to lower toward an unoccupied energy-saving setting. The graph shows a very clear step
Wireless Pneumatic Thermostat Evaluation
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change where the space temperature begins to lower immediately at that point. The downward slope of
that line is more gradual than the dramatic upward jump in the morning. This is due to the fact heat is being
lost at a slower rate through the window to cold outside air.
The graph shows space temperature falling until 6:00 a.m., when the WPT technology again calls for a rise in
space temperature back to its occupied setting.
This repeated pattern of low temperature during the unoccupied weekend, a steep rise when the HVAC
controls switch to occupied mode, followed by stable temperatures during the day, and concluding with a
gradual temperature decline of space temperature as it goes back to its unoccupied setpoint is clear
indication that the WPT technology is providing active energy saving control sequences on the building’s
pneumatic HVAC system.
Figure 8 depicts temperatures within the same eighth floor space, except this time it is an entire week of
data from a Monday through the following Sunday. The same pattern seen in Figure 7 is repeated here: a
very steep rise in temperature each weekday morning as the WPT technology begins an occupied period, a
relatively stable daytime temperature, and a gradual decrease in temperature for weekday nights and for
the weekend period.
Figure 8. Space Temperatures in an Eighth Floor Exterior Zone from January 6 Through
January 12, 2013 (nightly temperatures subfreezing). Note: These data are for the same space
depicted in Figure 7 except that it is an entire week of data from Monday through Sunday.
B. Economic Performance Results
With the WPT system’s technical performance validated, the team moved forward to determine the
economic viability of the technology. Because the goal of Green Proving Ground evaluations is not just to
provide a case study at one location but to provide information about a technology’s viability at facilities
Wireless Pneumatic Thermostat Evaluation
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around the country, energy models were used to evaluate the technology’s economics in a wide variety of
locations.
ORNL researchers used the DOE-2 energy analysis software as the platform to conduct the economic
evaluation. Within this platform, they looked at models of three standard building types. These models
were developed by Pacific Northwest National Laboratory and are used as a standard in many types of
energy comparative analyses. Descriptions of the models are in Table 1.
Figure 9 is a map of the 16 climate zones in which the three building types were modeled.
Figure 9. Map of the 16 Climate Zones in Which the Three Building Types Were Modeled.
The details of the energy modeling are given in Section IV.D. of this report, and results of the 48 iterations
(three building types in 16 climate zones each) are given in Appendix B. This section will now focus on the
economic viability of the technology and how individual site managers throughout the country can use the
data to determine whether this technology is appropriate for their sites.
To estimate the cost of installing a WPT system at a site, the vendor provided the following cost data.
•
Small office (5,500 ft2): $0.70 to $1.20 per square foot
•
Medium office (53,630 ft2): $0.60 to $1.10 per square foot
•
Large office: (498,500 ft2): $0.50 to $0.90 per square foot
Wireless Pneumatic Thermostat Evaluation
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The cost per square foot range is mainly driven by the density of thermostats in a building. The vendor has
seen some buildings with one thermostat for every 250 ft2 and other buildings with one per 1,000 ft2.
Offices with large open cubicle spaces tend to have lower thermostat density vs. offices with a lot of
enclosed rooms. The denser the thermostat count, the higher the cost naturally. The national average is
about one thermostat per 900 ft2, and 80% of the buildings are within ±15% of this density. This density
factor accounts for about 80% of the variability in per square foot installed cost.
Labor is a secondary factor affecting cost. In some older buildings with concrete walls instead of sheet rock,
it takes longer to mount the thermostats and connect the pneumatic tubes while maintaining aesthetics.
Also, local labor rates are higher in major cities. Overall, labor accounts for about 20% of the variability in
the per square foot cost.
The estimated cost is for a turnkey installation, including all material, software, and labor for a standalone
WPT system such as the one at WWC. To get the estimated cost for a turnkey installation, simply multiply
the facility’s respective square footage by the range of costs per square foot.
•
Small office: (5,500 ft2) × ($0.70 to $1.20 per ft2) = $3,850 to $6,600 installed cost.
•
Medium office: (53,630 ft2) × ($0.60 to $1.10 per ft2) = $32,200 to $59,000 installed cost.
•
Large office: (498,500 ft2) × ($0.50 to $0.90 per ft2) = $249,000 to $449,000 installed cost.
The next step to determine the technology’s economic viability at a site is to look at the potential energy
savings and the corresponding energy cost savings at a particular site. For demonstration purposes, this
section will look at the energy savings calculated by the model for a large office in Atlanta, Georgia. (Results
for all facilities and locations are shown in Appendix B.) Figure 10 shows the results for the large office in
Atlanta, Georgia.
Figure 10. Results of the Energy-Savings Calculations for the Large Office in Atlanta, Georgia.
Wireless Pneumatic Thermostat Evaluation
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For this example, look at the energy savings if the unoccupied setpoints were allowed to be 83°F in the
cooling season and 62°F in the heating season. The charts show that this facility can expect to save
404,503 kWh in the cooling season and 3,782,000 kBtu during the heating season.
According to the US Energy Information Administration (EIA) Electric Power Monthly online, the average
commercial electricity rate in Atlanta is $0.1059/kWh. To determine the energy cost savings during cooling
season associated with this technology, simply multiply the energy saved, 404,503 kWh, by the unit cost of
electricity, $0.1059/kWh.
•
404,503 kWh × $0.1059/kWh = $42,800/year in electricity cost savings.
The same process is used to calculate energy cost saving during the heating season. With a 62°F unoccupied
setpoint, the large office in Atlanta can expect to save 3,782,000 kBtu. The latest EIA natural gas price
surveys (2014) show the average commercial unit price of natural gas in Atlanta to be $10.77 per thousand
cubic feet. One thousand cubic feet of natural gas is equivalent to 1,000 kBtu, giving the gas unit price of
$0.01077/kBtu. Using the same process as calculating electricity cost savings, multiply the natural gas
amount saved by the unit cost.
•
3,782,000 kBtu × $0.01077/kBtu = $40,700 in natural gas cost savings.
Adding the electrical and natural gas annual cost savings gives a total of
•
$42,800 + $40,700 = $83,500 in annual energy savings by using the WPT and implementing an
occupied/unoccupied thermostat schedule that allows space temperatures to drift to 83°F in the
cooling season and 62°F in the heating season.
The final step to look at the WPT system’s economic viability is to compare the potential cost savings to the
cost of installing the technology. In the case of a large office in Atlanta, the installed cost was between
$249,000 and $449,000 (refer to installed cost calculations earlier in this section), with annual energy cost
savings of $83,500/year.
The most straightforward economic comparison is a technique called “simple payback.” It is simply dividing
the installed cost of technology by the annual savings per year. The result is the number of years it would
take for the technology to pay for itself with cost savings.
For the large office in Atlanta, the calculation would look like this:
•
Installed Cost: $249,000 to $449,000
•
Annual Energy Cost Savings: $83,500/year
•
Simple Payback Period: ($249,000 to $449,000) ÷ ($83,500/year) = 3.0 to 5.4 years
As a general rule, a simple payback period of less than 5 years is considered to be a strong indicator of
economic viability. The WPT technology in this situation shows a simple payback that is mostly within that
threshold, and it would be a viable option to save energy in this facility based upon energy savings.
These energy cost savings and simple payback calculations were performed on each of the three building
types in each of the 16 climate zones. The results are shown in Tables 2–4. It should be noted that as
Wireless Pneumatic Thermostat Evaluation
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discussed in Section IV.D., these savings are based solely on modeling the energy savings that would result
from a simple occupied/unoccupied thermostat schedule. If other control strategies were implemented,
which is quite possible with this technology, greater savings would result. The greater energy cost savings
would result in even lower simple payback periods.
Table 2. Tabulated Data for Large Office Buildings
Climate
Zone
1A
2A
2B
3A
3B-coast
3B
3C
4A
4B
4C
5A
5B
6A
6B
7
8
City
Miami, FL
Houston, TX
Phoenix, AZ
Atlanta, GA
Los Angeles, CA
Las Vegas, NV
San Francisco, CA
Baltimore, MD
Albuquerque, NM
Seattle, WA
Chicago, IL
Boulder, CO
Minneapolis, MN
Helena, MT
Duluth, MN
Fairbanks, AK
Annual
Annual
Unit Cost
Electricity
Electricity
of
Cost
Savings
electricity
Savings
(kWh/year) ($/kWh)
($/year)
615,750
502,786
235,378
404,503
305,511
145,671
152,772
332,204
116,220
125,012
170,974
93,652
160,618
81,368
88,482
73,889
0.10
0.08
0.11
0.11
0.27
0.09
0.17
0.11
0.11
0.08
0.09
0.11
0.10
0.01
0.10
0.18
61,206
40,625
25,115
42,837
51,418
13,722
25,712
37,207
12,656
9,538
15,131
10,452
16,512
7,811
9,076
13,130
Annual
Annual
Total
Heat
Unit Cost
Natural Gas Annual
Energy of Natural
Cost
Energy Cost
Saved
Gas
Savings
Savings
(1,000
($/MCF)
($/year)
($/year)
Btu/year)
651,502
11.99
7,812
69,017
2,828,689
9.23
26,109
66,734
2,960,910
9.95
29,461
54,576
3,782,439
10.77
40,737
83,574
4,158,290
8.90
37,009
88,426
4,010,482
8.35
33,488
47,210
6,313,901
8.90
56,194
81,905
4,359,986
12.05
52,538
89,745
4,137,753
8.12
33,599
46,255
6,625,027
8.97
59,426
68,965
4,924,071
13.07
64,358
79,489
4,569,352
8.72
39,845
50,296
4,567,715
8.20
37,455
53,967
5,085,454
10.86
55,228
63,039
5,875,484
8.20
48,179
57,255
6,920,554
6.68
46,229
59,359
Simple Payback
Range (years)
Low
Mid High
3.6
3.7
4.6
3.0
2.8
5.3
3.0
2.8
5.4
3.6
3.1
5.0
4.6
3.9
4.3
4.2
5.1
5.2
6.4
4.2
3.9
7.4
4.3
3.9
7.5
5.1
4.4
6.9
6.5
5.5
6.1
5.9
6.5
6.7
8.2
5.4
5.1
9.5
5.5
5.0
9.7
6.5
5.6
8.9
8.3
7.1
7.8
7.6
Table 3. Tabulated Data for Medium Office Buildings
Climate
Zone
1A
2A
2B
3A
3B-coast
3B
3C
4A
4B
4C
5A
5B
6A
6B
7
8
City
Miami, FL
Houston, TX
Phoenix, AZ
Atlanta, GA
Los Angeles, CA
Las Vegas, NV
San Francisco, CA
Baltimore, MD
Albuquerque, NM
Seattle, WA
Chicago, IL
Boulder, CO
Minneapolis, MN
Helena, MT
Duluth, MN
Fairbanks, AK
Annual
Annual
Unit Cost
Electricity
Electricity
of
Cost
Savings
electricity
Savings
(kWh/year) ($/kWh)
($/year)
73,391
54,318
41,878
44,438
24,761
27,783
13,324
35,813
15,656
10,314
14,201
10,778
13,649
8,660
7,695
6,884
0.10
0.08
0.11
0.11
0.17
0.09
0.17
0.11
0.11
0.08
0.09
0.11
0.10
0.10
0.10
0.18
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7,295
4,389
4,468
4,706
4,167
2,617
2,242
4,011
1,705
787
1,257
1,203
1,403
831
789
1,223
Annual
Annual
Total
Heat
Unit Cost
Natural Gas Annual
Energy of Natural
Cost
Energy Cost
Saved
Gas
Savings
Savings
(1,000
($/MCF)
($/year)
($/year)
Btu/year)
118,271
11.99
1,418
8,713
305,767
9.23
2,822
7,211
363,045
9.95
3,612
8,081
422,769
10.77
4,553
9,259
512,587
8.90
4,562
8,729
457,809
8.35
3,823
6,440
695,133
8.90
6,187
8,429
483,341
12.05
5,824
9,835
455,525
8.12
3,699
5,404
716,035
8.97
6,423
7,210
551,537
13.07
7,209
8,465
507,275
8.72
4,423
5,626
516,123
8.20
4,232
5,635
572,151
10.86
6,214
7,045
648,993
8.20
5,322
6,111
745,442
6.68
4,980
6,203
Simple Payback
Range (years)
Low
Mid High
3.7
4.5
4.0
3.5
3.7
5.0
3.8
3.3
6.0
4.5
3.8
5.7
5.7
4.6
5.3
5.2
5.2
6.3
5.6
4.9
5.2
7.1
5.4
4.6
8.4
6.3
5.4
8.1
8.1
6.5
7.5
7.3
6.8
8.2
7.3
6.4
6.8
9.2
7.0
6.0
10.9
8.2
7.0
10.5
10.5
8.4
9.7
9.5
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Table 4. Tabulated Data for Small Office Buildings
Climate
Zone
1A
2A
2B
3A
3B-coast
3B
3C
4A
4B
4C
5A
5B
6A
6B
7
8
City
Miami, FL
Houston, TX
Phoenix, AZ
Atlanta, GA
Los Angeles, CA
Las Vegas, NV
San Francisco, CA
Baltimore, MD
Albuquerque, NM
Seattle, WA
Chicago, IL
Boulder, CO
Minneapolis, MN
Helena, MT
Duluth, MN
Fairbanks, AK
Annual
Annual
Unit Cost
Electricity
Electricity
of
Cost
Savings
electricity
Savings
(kWh/year) ($/kWh)
($/year)
20,014
13,645
12,769
9,661
5,368
10,091
4,448
6,098
6,599
3,839
4,828
4,672
4,391
4,311
3,235
3,069
0.10
0.08
0.11
0.11
0.17
0.09
0.17
0.11
0.11
0.08
0.09
0.11
0.10
0.10
0.10
0.18
1,989
1,103
1,362
1,023
903
951
749
683
719
293
427
521
451
414
332
545
Annual
Annual
Total
Heat
Unit Cost
Natural Gas Annual
Energy of Natural
Cost
Energy Cost
Saved
Gas
Savings
Savings
(1,000
($/MCF)
($/year)
($/year)
Btu/year)
374
11.99
4
1,994
23,653
9.23
218
1,321
16,683
9.95
166
1,528
41,961
10.77
452
1,475
15,577
8.90
139
1,042
33,884
8.35
283
1,234
50,690
8.90
451
1,200
60,704
12.05
731
1,414
48,446
8.12
393
1,112
66,823
8.97
599
892
72,223
13.07
944
1,371
58,412
8.72
509
1,031
72,946
8.20
598
1,050
68,815
10.86
747
1,161
86,390
8.20
708
1,040
106,190
6.68
709
1,255
Simple Payback
Range (years)
Low
Mid High
1.9
2.9
2.5
2.6
3.7
3.1
3.2
2.7
3.5
4.3
2.8
3.7
3.7
3.3
3.7
3.1
2.6
4.0
3.4
3.5
5.0
4.2
4.4
3.7
4.7
5.9
3.8
5.1
5.0
4.5
5.0
4.2
3.3
5.0
4.3
4.5
6.3
5.4
5.5
4.7
5.9
7.4
4.8
6.4
6.3
5.7
6.3
5.3
Another operating cost associated with any technology is the cost to maintain that technology. Looking at
maintenance required by the existing conventional pneumatic thermostats and the new WPT system, there
was no indication that there is any difference in maintenance required by either system. They both are
robust and reliable.
VI. Summary Findings and Conclusions
A. Overall Technology Assessment at Demonstration Facility
The WPT technology proved itself capable of implementing energy-saving control strategies at facilities that
are currently controlled by pneumatic control systems. The technology passed the performance test
conducted in this evaluation.
It also shows indications that it would be economically viable in a wide variety of facilities around the
country. Individual circumstances will have to be evaluated for each site that is considering this technology.
This technology should be recommended for implementation at facilities that currently are using
conventional pneumatic control systems on their HVAC systems.
B. Best Practice
The WPT technology should be considered a best practice for facilities that currently use conventional
pneumatic control systems with their HVAC systems. It represents an economically viable technology that
can reduce HVAC energy consumption. This will result in lower energy costs and lower greenhouse gas
emissions for the respective facilities.
Also, a best practice before installing the WPT technology would be to perform preinstallation tests to
determine how well wireless signals can be transmitted through the building. Different construction types
can interfere with signal transmission.
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C. Barriers and Enablers to Adoption
There are no market barriers that would prevent the adoption of this technology. Based on this evaluation,
it provides a valuable service by enabling energy-saving HVAC control strategies to be implemented on
buildings that already have a properly functioning pneumatic system.
D. Recommendations for Installation, Commissioning, Training, and Change Management
This technology should have a useful service life of more than 10 years. This estimate is based upon the
nature of the components used to manufacture the system and their historic service lives.
As with any new technology, a certain level of training would be required for facility operators to learn how
to manage the technology. The vendor offers a training class that lasts 1 day.
VII. Appendices
A. Detailed Technology Specification
Wherever possible, describe technology in terms of generic performance criteria, and refrain from providing
vendor-specific images and proprietary data.
B. Research Details
This appendix has summary graphs that show the energy-saving results for each of the three modeled
buildings (large office, medium office, and small office) within each of the 16 cities. Data from these graphs
and tables can be used to estimate energy savings in the same fashion that was described in Section V.B.,
“Economic Performance Results.”
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